The invention relates to a railway sewing system for sewing and piecing together of two free ends of separate sheets of fabric across the full width thereof joining same as one piece for subsequent processing in a textile plant. More particularly, the invention relates to stitch multiplier apparatus for adjustably and automatically multiplying the number of stitches at the selvedges of the fabric for additional strength where the forces on the joint tend to be concentrated.
Heretofore, arrangements have been utilized which include a horizontal extending fabric support along which a sewing head employing a sewing machine moves to stitch ends of the two fabric sheets together. Typically, the drive for the traversing movement of the head and the drive for the sewing machine itself are transmitted by a single A.C. type drive motor. Since it is desired to drive the sewing machine at a constant rate, the output of the drive motor is controlled to produce a separate constant drive for sewing and a variable speed for the traversing head drive. The drive motion taken off of the shaft of the drive motor for the traversing sewing head is normally transmitted by sprocket and chain drives which are stepped down by means of a final worm gear drive along which the sewing head moves. However, in order to slow down the travel speed of the sewing head in the region of the selvedges to multiply the stitches, complicated clutch systems have been utilized having a large number of mechanical parts which influence reliability and requires considerable maintenance. Electromagnetic clutches have been employed which are controlled by feeler switches which sense the presence of the sewing head in the selvedge region and shift the chain drive to a slower transmission speed. Moreover, the environment of such mechanical arrangements and their required lubrication is not entirely compatible nor satisfactory for the sewing of fabric which easily can be soiled.
Accordingly, an important object of the present invention is to provide apparatus for sewing the ends of two separate fabric sheets together and automatically multiplying the number of stitches in the selvedge region of the fabric which is greatly simplified in its control and construction affording increased reliability.
Another important object of the present invention is to provide apparatus for sewing the ends of the two separate fabric sheets together which has fewer mechanical parts and presents a cleaner work environment for the sewing and processing of textile fabric.
Specifically, the object of the present invention is to provide railway sewing apparatus having a simplified drive transmission for the traversing sewing unit and control of the rate of speed of the sewing unit to multiply the stitch rate at the selvedge which is achieved by reliable electronic control of the input to the drive motor which may be varied electronically.